1. Field of the Invention
The invention relates to an airbag for installation in a motor vehicle.
2. Description of Related Art
Traditionally, airbags are provided with one or several outflow openings and are filled by means of a gas generator unit with a specified performance profile. Because of the geometry of the airbag, the performance profile of the gas generator unit, the cross-section of the outflow opening or openings, and the internal pressure of the airbag a certain firmness results when it is inflated.
Ideally, the hardness of an airbag, in particular the firmness of an airbag used in a side airbag system, should be adapted to the body weight of the vehicle occupants. A relatively light occupant requires an airbag with less firmness, in other words with lower internal pressure, so that the force exerted by the airbag is as low as possible when the relevant part of the body, for example the upper part of the torso (i.e. thorax), strikes the airbag. Heavier vehicle occupants, on the other hand, require an airbag with greater internal pressure, otherwise the overall retaining pressure for the occupant may be too low and there is a risk that the occupant will strike the structure of the vehicle despite the presence of the airbag.
It is generally not possible to design each airbag in a vehicle to accord with the requirements of the specific occupants to be protected, as a vehicle is generally used by several people. It would therefore be desirable to have an airbag which “recognizes” if it has to protect a light or a heavy occupant and which is configured to provide different hardnesses as required.
In addition, a similar problem to the one described above also arises in the case of so-called “out of position occupants”. Airbags are generally designed in such a way that they protect vehicle occupants who are in a “normal” seating position. If the occupant is in an atypical seating position, he or she may find his or herself in the direction of expansion of the airbag, resulting in a possibility of injury. U.S. Pat. No. 6,783,151 proposes an airbag which accommodates an occupant positioned in the direction of expansion of the airbag, and limits the expansion of the airbag in response. Multiple embodiments of U.S. Pat. No. 6,783,151 accommodates an out of position occupant.
In a first embodiment, the airbag includes two chambers, which are connected with each other by a valve arrangement. This valve arrangement is designed and implemented in such a way that the valve remains closed or restricted if the airbag strikes an obstacle during expansion. In this case, only one chamber of the airbag is filled, so that the direction of expansion is shortened.
In another embodiment, the outer cover of the airbag includes a valve which is only closed if the airbag does not meet an obstacle. If the airbag does meet an obstacle, the valve remains open, keeping the expansion and pressure in the airbag low.
The airbag embodiments proposed in U.S. Pat. No. 6,783,151 serve to limit the expansion of the airbag in the presence of an obstacle. The type of obstacle, for example, whether the vehicle occupant is large and heavy or small and light, does not play a role. Such factors are also not necessary in order to solve the task of the present invention.
The task of the present invention is to create an airbag which provides a different firmness depending on certain physical characteristics of the vehicle occupants.